Dithiane-l-oxide

To a cooled solution of dithiane (1) (2.00 g, 16.7 mmol) in methanol (125 ml) was added an aqueous solution (35 ml) of sodium periodate (3.68g, 17.5 mmol) at such a rate (approximately 30 min) to maintain the temperature at 20°C. Stirring and cooling were continued for an additional 30 min. The reaction mixture was then filtered to remove sodium iodate. and the resulting solution taken to near dryness on a rotary evaporator. Extraction of the solids with chloroform produced a solution which was dried over sodium sulfate, and filtered. Evaporation left the crystalline sulfoxide (2) (2.13g, 94%), m.p. 86-87°C. 

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Boron nitride modified with 1,3-dithiane-l-oxide (7.4 wt%). Boron nitride alone also showed no activity. 

To understand the origin of this high catalytic activity and the enantioselectivity a series of computer simulation studies was carried out to determine the most favourable locations for 1,3-dithiane-l-oxide (R=H and... 

Bohman and Allenmark resolved a series of sulphoxide derivatives of unsaturated malonic acids of the general structure 228. The classical method of resolution via formation of diastereoisomeric salts with cinchonine and quinine has also been used by Kapovits and coworkers " to resolve sulphoxides 229, 230, 231 and 232 which are precursors of chiral sulphuranes. Miko/ajczyk and his coworkers achieved optical resolution of sulphoxide 233 by utilizing the phosphonic acid moiety for salt formation with quinine. The racemic sulphinylacetic acid 234, which has a second centre of chirality on the a-carbon atom, was resolved into pure diastereoisomers by Holmberg. Racemic 2-hydroxy- and 4-hydroxyphenyl alkyl sulphoxides were separated via the diastereoisomeric 2- or 4-(tetra-0-acetyl-D-glucopyranosyloxy)phenyl alkyl sulphoxides 235. The optically active sulphoxides were recovered from the isolated diastereoisomers 235 by deacetylation with base and cleavage of the acetal. Racemic 1,3-dithian-l-oxide 236... 

Page et al. (see [298] and references therein) have shown that generally excellent stereocontrol in organic reactions can be obtained by using DITOX (1,3-dithiane-l-oxide) derivatives as chiral auxiliaries. The one-pot stereo-controlled cycloalkanone synthesis given here outlines some aspects of the chemistry worked out for efficient acylation-alkylations steps. Of note are the use of N-acyl imidazoles under mixed base (sodium hexamethyldisilazide/n-butyllithium) conditions to yield the lithium enolates of 2-acyl-l,3-dithiane-l-oxides) and the sequential alkylation-cyclization of the latter (steps (iv) and (v)). 

Both enantiomers of the 2-ethyl- 1,3-dithiane-l -oxide starting material may be prepared selectively in up to optical purity. The aminated products are of interest as potential synthons for chiral synthesis of both enantiomers of a-amino acids. 

The use of ethyl ethylthiomethyl sulphoxide in this reaction leads to the desired addition products in much better yields (95-97%). These products were then converted into ketene dithioacetal monoxide derivatives 430 by a sequence of reactions (equation 258)505. Reaction of 2-lithio-l,3-dithiane-l-oxide with benzophenone affords a mixture of the diastereoisomeric tertiary alcohols 431 in a ratio which is temperature dependent (cis trans changes from 3 1 at — 78 °C to 1 1 at room temperature)268. 

Zeolite Y modified with (+/-)-l,3-dithiane-l-oxide, 1 molecule per super cage... 

A series of 2- and 2,5-disubstituted 1,3-dithianes when oxidized in wet MeCN, using Pt electrodes in an undivided cell, provided 1,2-dithiolane-l-oxides selectively and in good yields, as in Eq. (89) [139]. These 1-oxides had not been observed in previous studies, when divided cells were used. 

Sehr mild ist die Methode, 2-substituierte 1,3-Dithian-S-oxide mit Triethyloxonium-te-trafluoroborat zu 2-substituierten 1-Ethoxy-l, 3-dithianium-tetrafluoroboraten umzuset-zen, die mit Wasser zu Aldehyden gespalten werden365. 

The 1,3-dithiane-l,3-dioxides can also be prepared by sodium periodate oxidation of the 1,3-dithiane, and the trans isomer was thus obtained in a 58% recrystallized yield [81]. Chiral molecules of this type (C2 symmetry) are particularly suitable for use as chiral acyl anion equivalents [11,82]. 

The effect of sulphur oxidation on the transmission mechanism of Vhh couplings in a series of 1,3-dithiane derivatives has been studied by Gauze et The results have been rationalized in terms of the hyperconjugation interactions involving the S=0 group the compounds studied were 1,3-dithiane-1-oxide, cj5-l,3-dithiane-l,3-dioxide, 1,3-dithiane-1,1,3-trioxide and 1,3-dithiane-l, 1,3,3-tetraoxide. 

Besides 1,3-oxathianes, the 1,3-dithiane 1-oxide moiety can be used for directing the nucleophilic addition of an organometallic reagent to a carbonyl group in a diastereoselective manner. The addition of methylmagnesium iodide to the 2-acyl-l,3-dithiane 1-oxide 23A leads exclusively to the diastereomer which is formed by Re-side attack. On the other hand, addition... 

The formation of S-oxides has also been observed when oxidizing a variety of 5-substituted 2-tert-butyl-l,3-dithianes in wet acetonitrile. In an undivided cell, 4-substituted 1,2-dithiolane-l-oxides were oblained (Scheme 25) [113]. A coupled cathodic process, in this case, was the reduction of protons formed in the anodic reaction. 

Scheme 25 Conversion of 1,3-dithianes into 1,2-dithiolane-l-oxides.

As expected, 2-halo-l,3-dithianes react with nucleophiles under Sn conditions. Suitable nucleophiles are enamines <2002TL9517, 2004T6931> and phenols <1997MOL7>. The reaction with EtOC(S)S K, followed by oxidation, provided a xanthate which generated a 1,3-dithiane 1-oxide radical upon treatment with Bu3SnH (Scheme 69) <2004T7781>. An efficient one-carbon radical precursor has also been obtained by addition of 2,2,6,6-tetramethyl-piperidine-l-oxyl (TEMPO) to 2-lithio-l,3-dithiane. The reactivity of this compound has been demonstrated <2005S1389>. 

The chemistry of chiral 1,3-dithiane 1-oxides, in particular their use as chiral auxiliaries, has been reviewed <19980PP145>. Some further developments in this field are the stereoselective a-alkylation with alkyl halides <1997T13149> or a-hydrazination with di-fert-butyl azodicarboxylate (DBAD) <2000T9683>. The carbonyl group of 2-acyl-l,3-dithiane 1-oxides was also used as an electrophile (Scheme 82). Interestingly, acyclic enolates react with these substrates to give a 95 5 mixture of anti- and ry -adduct, whereas cyclic enolates produce a mixture of anti- and ry -adduct in 8 92 ratio <2000JOC6027>. 

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